1. Field of the Invention
This invention relates to refrigerant recovery system, which is used for recovering gas and liquid refrigerants from air-conditioning and refrigeration systems, reclaiming used refrigerants into a recovery tank for recycling.
2. Description of the Prior Art
The HVACR industries had undergone a gigantic change since the phase out of ozone-depleting chlorofluorocarbon (CFC)-based refrigerants. In part of this U.S. clean air acts, we required to reclaim all refrigerants. Venting refrigerant into our air is no longer allowed. To comply with this earth shaking new law, a recovery system is needed for recovering refrigerants. Nevertheless, most technicians handling refrigerants are honestly complying with this new law. However, the sincere motivation to comply with the law is frequently failed due to the recovery systems often not doing it job well.
The recovery systems currently available in the industry have two common problems, the recovering speed is too slow and the pressure rapidly build up in the recovery tanks which is up to a dangerous level. The high pressure in the recovery tank not only slow down the recovery process, it also can be fatal as well to people whom close by if explosion ever occur. A pressure relief valve equipped in the tank can safeguard the tank in a safety pressure level by releasing refrigerant into the air when excessive pressure present inside the tank. It is legal to vent refrigerants into the air with this manner, but it is not good for our environment.
There are good chances that the refrigerant of an unit being recovered was partially recovered and the rest of the refrigerant remained in the unit was vented into our atmosphere, creating a long-term environmental problem. It is impossible to completely recover refrigerant if the recovery tank has excessive pressure. It slows down the recovery speed and the excessive pressure can burst the recovery tank as well. If this ever happens, the entire refrigerant in the recovery tank will be escaped out from the recovery tank.
Refrigerants can not be recovered into the recovery tank if pressure is too high inside the tank; even the tank is not full according to its capacity by weight. Nonetheless, all recovery system can easily handle refrigerants from small appliances such as home refrigerators, which contain small amount of refrigerants. To recover refrigerant from a small appliance, the pressure build up inside the recovery tank was not high enough to significantly block refrigerant flow into the recovery tank, if the recovery tank was at the room temperature at the beginning. But it is a different phenomena if a larger amount of refrigerant to be recovered. There will be fewer refrigerants recovered into the tank when the pressure differential decreases due to the pressure rapidly built up in the recovery tank. Sooner or later, there will be no refrigerant flowing into the recovery tank even the recovery pump keep running. Under this circumstance, the recovery pump can be burned since it works under intolerable high pressure.
The more powerful recovery pumps were install for some of the recovery systems attempted to overcome this high-pressure built up. Unfortunately, a bigger pump does not recover refrigerant much faster once the recovery tank pressure close to the pump discharged pressure. When the recovery tank pressure reach the pump discharge-pressure, there shall be no more refrigerants flow into the tank. Most likely, refrigerant will escape from the relief valve at this time. Otherwise, a more powerful recovery pump adds higher pressure into the recovery tank could be well beyond the safety level. This means a higher risk for people handling the recovery tank because of high internal tank pressure.
As the pressure increase, the heat also increases. The recovery tank can be exploded with the excessive pressure and heat built up in the tank. To avoid accident, high-pressure cutouts are installed for many recovery machines. During the high-pressure cutout, the recovery machine is not capable for operation. Some recovery system manufactures consider this problem with another approach by pre-cooling the refrigerant before it gets into the recovery tank by passing through a coil and cools it by fanning air through the coil. The high-pressure rapid built up in the recovery tank still an unsolved problem. Additionally, the cooling coil creates a very big problem by adding air into the recovery tank. The coil contents a large volume of air at the discharged side of the recovery pump. The air pocket in the cooling coil needs to be removed by another pump (almost never happen). Otherwise, the air was just pushed into the recovery tank mix with refrigerant. The refrigerant is contaminated with air and this is an explosive combination.